JPH0791471A - Disk brake rotor having excellent thermal-shock resistance - Google Patents

Abstract

PURPOSE:To suppress the generation of a heat crack owing to a thermal-shock by a method wherein the corner part of the tip of a disc brake rotor is formed in a curved shape and surface coarseness is set to a specified value or less. CONSTITUTION:Three kinds of disc brake rotors, such as all four corners are formed in a curved shape, two corners on the outer side are formed in a curved shape, two corners on the inner side are processed in a C-shape, and all four corners are processed in a C-shape, wherein the shapes of the corner part of the tip of an outer slide surface 2 and the corner part of the tip of an inner slide surface 3 are different from each other are manufactured to execute a heat crack generation test. As a result, the disc brake rotor wherein the corners of the tip are all formed in a curved shape has the number of the heat cracks which is less than that of a compared good. This constitution relaxes concentration of a stress owing to a thermal shock in a way that the corner part of the tip is formed in an R-shape. Further, as a result of a thermal-shock test regarding coarseness of the corner part of the tip being executed, a smooth surface (2.5S or less) has the number of the heat tracks being less than that of a coarse surface and the more surface coarseness is higher, the more the frequency of the generation of the heat track is remarkably further often.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake rotor which is a brake component for vehicles, particularly sports vehicles, and which is excellent in thermal shock resistance.

[0002]

2. Description of the Related Art A disc brake rotor for a vehicle, particularly a sports vehicle, has a structure as shown in FIG. 3, which is a sectional view taken along line AA of FIG. The disc brake rotor 1 has an outer sliding surface 2 and an inner sliding surface 3 that are pressed by a brake pad, both of which are integrally formed, and the fins 4 slide on the outer surface in order to achieve heat dissipation. It is connected to the moving surface 2 and the inner sliding surface 3. A void 5 is formed around the fin 4 to promote heat dissipation.
In FIG. 3, the tip corner portion 6 of the disc brake rotor 6
Normal surface processing C0.2-0.5 (mm) is given to 7, 8, and 9.

The disc brake rotor 1 is usually made of flake graphite cast iron of FC20 which is excellent in so-called braking performance such as damping ability and natural vibration.
Repeatedly, fine thermal cracks (heat cracks) occur on the sliding surface of the disc brake rotor pressed by the brake pad. In Japanese Utility Model Application Laid-Open No. 57-122460, it is proposed to inject compressed air to a brake component during braking to prevent its overheating and to prevent early wear and heat cracking.

[0004]

By the way, particularly in sports cars, since braking is frequently performed during high-speed running, a considerable number of heat cracks due to thermal shock are generated on the sliding surface of the disc brake rotor held by the brake pads. Occur. These heat cracks are fine,
If it continues to be used as it is, it contains a serious factor that may cause damage to the disc brake rotor.
For this reason, regarding the disc brake rotor, compressed air is sprayed or the like from the viewpoint of the material and for promoting heat dissipation as described above, but it has reached the present state without a solution. It should be noted that promotion of heat dissipation by the fins 4 shown in FIG.

[0005]

As a result of earnest studies on the heat crack due to the thermal shock generated on the sliding surface of the disc brake rotor, the inventor has found that it is possible to change the shape of the tip corner of the disc brake rotor. The present invention has been achieved by finding that it has a great effect on crack suppression. The present invention is characterized in that the tip corner portion of the disc brake rotor held by the brake pad is formed into an R (curved surface) shape. Although the size of R may be slightly different depending on the thickness of the rotor portion of the disc brake rotor, a curved surface of R 0.2 to 0.5 (mm) may be formed, and the thickness of R is approximately half the thickness of the disc brake rotor. If an R shape is given, an effect of suppressing heat crack can be expected. The surface roughness of the R-shape imparting portion is 2.5 S or less.

The material of the disc brake rotor of the present invention is iron, inevitable impurities and weight ratio of carbon 3.5 to 3.5.
3.9%, silicon 2.3-3.0%, manganese 0.7-
1.10%, phosphorus 0.05% or less, sulfur 0.08 to 1.
14%, copper 0.7-1.2%, CE value 4.3-4.
7 and tensile strength 100 N / mm ² (10 kg / mm
² ) Flake graphite cast iron having a hardness of HB130 or more.
The reasons for limiting the component composition (% by weight) are as follows. Carbon: 3.5 to 3.9% Generally, carbon is an element that improves the thermal conductivity of cast iron,
The carbon content in the disc brake rotor material of the present invention is 3.5% or more. Coarse graphite precipitates as the amount of carbon increases, the strength decreases, and the thermal crack resistance is impaired. Therefore, the upper limit of carbon was set to 3.9%. Silicon: 2.3 to 3.0% Silicon dissolves in the matrix structure of cast iron to lower the thermal conductivity, so the upper limit is 3.0%, and good flake graphite is deposited, which is good. The lower limit is 2.3% in order to maintain wear resistance. Manganese: 0.7 to 1.10% In order to maintain the strength, the lower limit is set to 0.7%, and in order to suppress precipitation of MnS, which hinders the toughness in the matrix, the upper limit is set to 1.
It was set to 10%. Phosphorus and sulfur: Phosphorus and sulfur are inevitably contained, but both elements cause embrittlement of the material, so the phosphorus content was set to 0.05% or less, and sulfur 0.08 to 0.14%. Copper: 0.7% or more to stabilize the pearlite base,
The effect cannot be expected even if the content is 1.2% or more, so the upper limit was made 1.2%.

[0007]

Embodiments and Functions The embodiments of the present invention will be described below. (Example 1) Flake graphite cast iron material (C3.7%, Si2.5
%, Mn 0.8%, Cu 0.8%), the disk brake rotor of the present invention shown in FIGS. 1 and 2 and the conventional disk brake rotor shown in FIG. These were held in a heat treatment furnace at 650 ° C. (atmosphere temperature) for 1 hour, then taken out of the furnace and immersed in a water tank. After cooling to room temperature, it was dried, and the number of heat cracks generated on the sliding surface of the disc brake rotor was counted by color check, and the average value was calculated. The results are shown in Table 1.

[0008]

[Table 1]

In Table 1, in the comparative example of the disc brake rotor shown in FIG. 3, the tip corners 6C (outside) and 7C (inside) of the outer sliding surface 2 and the tip corner 8C ( C) is applied to all of the outer side) and 9C (inner side). In the disc brake rotor shown in FIG. 1 which is an embodiment of the present invention, the tip sliding edge portions 6R (outer side) and 7R (inner side) of the outer sliding surface 2 and the tip corner portion 8R ( All of the outer side) and 9R (inner side) are formed in an R shape. Further, a disc brake rotor shown in FIG. 2 which is another embodiment of the present invention has a tip corner portion 6R (outer side) of the outer sliding surface 2 and a tip corner portion 8R (outer side) of the inner sliding surface 3. It is formed in an R shape, and the tip corners 7C (inside) and 9C (inside) are C-processed. In Table 1, the number of heat cracks is smaller in each of the cases in which the tip corner portion is formed in the R shape than the number of heat cracks in the comparative product. It is considered that this is because it is possible to reduce stress concentration due to thermal shock by forming the tip corner portion into an R shape, and thus it is possible to reduce the occurrence of heat cracks.

(Embodiment 2) Referring to FIG. 3,
Tip corners 6C (outside) and 7C (inside) of the outer sliding surface 2,
And 9C (inside) of the tip corners 8C (outside) of the inner sliding surface 3 are unprocessed corners, and the rough surface and the smooth surface (2.
Three kinds of 5S) were manufactured from the same material as in Example 1, and the same heat treatment as in Example 1 was performed, and it was confirmed whether heat cracks due to thermal shock due to water cooling occurred. As a result, in the case of a rough surface, the number of outer diameter cracks was 18 on average, whereas in the case of a 2.5S smooth surface, the number of cracks was 1. From this, it is assumed that the larger the surface roughness is, the more remarkable the generation of heat cracks is. Although the disc brake rotor for sports cars has been described above, it goes without saying that the present invention can be applied to disc brake rotors for other vehicle types, and even if it is applied, it does not matter.

[0011]

As described above, according to the present invention, the tip corner portion of the disc brake rotor pressed by the brake pad is formed into an R (curved surface) shape and the surface roughness is 2.5 S or less. Therefore, there is an effect that the generation of heat crack due to thermal shock can be suppressed.

[Brief description of drawings]

FIG. 1 is a diagram showing a disc brake rotor according to an embodiment of the present invention at a cross-sectional position AA in FIG. 4, in which all of the tip corners of its sliding surface are formed in an R shape.

FIG. 2 is a disc brake rotor of another embodiment of the present invention at the AA cross-section position of FIG. 4, in which the outer tip corner portion of the outer sliding surface and the outer tip corner portion of the inner sliding surface are provided. It is a figure which shows the state formed in R shape.

FIG. 3 is a cross-sectional view of a conventional disc brake rotor, showing a state where the tip corners of the outer sliding surface and the inner sliding surface are C-machined.

FIG. 4 is a perspective view of a conventional disc brake rotor.

[Explanation of symbols]

 1 Disc Brake Rotor 2 Outer Sliding Surface 3 Inner Sliding Surface 4 Fins 5 Gap 6 Outer Tip Corner of Outer Sliding Surface 7 Inner Tip Corner of Outer Sliding Surface 8 Outer Tip Corner of Inner Sliding Surface 9 Inner tip corner of inner sliding surface

Claims (3)

[Claims] 1. A disc brake rotor characterized in that a tip corner portion of the disc brake rotor pressed by a brake pad is formed into an R (curved) shape. 2. The disc brake rotor according to claim 1, wherein the R-shaped portion has a surface roughness of 2.5 S or less. 3. The chemical composition is iron and inevitable impurities in a weight ratio of carbon 3.5 to 3.9%, silicon 2.3 to 3.0%,
0.7 to 1.10% of manganese, 0.05% or less of phosphorus, 0.08 to 0.14% of sulfur, 0.7 to 1.2% of copper, and a CE value of 4.3 to 4.7%. The disc brake rotor according to claim 1 or 2, characterized in that: